The present invention generally relates to fuse holders and power supply back-up systems, and more particularly to a fuse holder which is inserted in a power source line of a storage battery and a power supply back-up system using such a fuse holder.
In a point of sales (POS) terminal, a power source of a memory which stores sales data and the like is backed up by a storage battery. In the case of a POS terminal having a memory with a large memory capacity, a large amount of data stored in the memory must be backed up using the storage battery, and in this case, the storage battery used must have a large current capacity and a high output voltage. Particularly in such a case where the storage battery used has the large current capacity and the high output voltage, it is necessary to take measures so as to ensure safety when replacing the storage battery and to prevent a short-circuit accident when mounting the storage battery on the POS terminal. For this reason, a fuse holder is inserted in a power source line of the storage battery.
FIG. 1 shows an example of a conventional fuse holder used in the POS terminal. In FIG. 1, a first contact 12 and a second contact 18 are respectively held on right and left inner walls of a holder casing 20 in a confronting arrangement. A charge/discharge line 10 of a storage battery (not shown) for backing up a memory is connected to the first contact 12. On the other hand, a charge line 14 for memory back-up and a discharge line 16 are connected to the second contact 18. A sealed type fuse 22 is fit between the first and second contacts 12 and 18. Hence, the coupling of the charge/discharge line 10 with the charge line 14 and the discharge line 16 is disconnected by melting the fuse 22.
However, the charge line 14 and the discharge line 16 are coupled in common to the fuse 22 via the second contact 18, and the potentials at the charge line 14 and the discharge line 16 become the same. For this reason, if the fuse 22 is not set between the first and second contacts 12 and 18 or the fuse 22 is melted for some reason, it is impossible to detect this state from the outside during operation of the POS terminal. Because it is impossible to detect whether or not the fuse 22 is melted from outside the holder casing 20, it is necessary to stop the operation of the POS terminal and remove the fuse 22 for testing or inspection in order to positively check the state of the fuse 22. However, such an operation is troublesome to carry out, particularly because of the need to stop the operation of the POS terminal. But when such a troublesome operation is not carried out, there is a problem in that the important data stored in the memory may be lost when a power failure occurs because the fuse 22 may be in an abnormal state, that is, not set in the holding casing 20 or melted.